Many difficult to heal wounds, particularly where there is damage to the blood circulation system, are now treated with a gas such as oxygen to supplement the oxygen to the wound area that is not being satisfied by the damaged blood circulation system. Initially, this was done by installing a gas chamber around the wound and flowing oxygen continuously over the wound area. These chambers were rigid, heavy, difficult to clean between uses, and uncomfortable for the patient. Recently it has been discovered that continuous flow of oxygen is not necessary, and that effective hyperbaric treatment can be obtained by using a single adequate stationary charge of oxygen that is retained in a flexible chamber in contact with the wound for the treatment period. Unlike the continuous flow type devices, these devices do not need to be continuously attached to the oxygen supply during treatment, allowing mobility for the patient.
Many flexible topical hyperbaric bags are known. U.S. Pat. No. 5,154,697 assigned to Topox, Inc. discloses a hyperbaric bag that has a hole through the side of the bag that is to be exposed to the area to be treated. The periphery of the hole is reinforced with a strong ring. A belt structure affixes the bag over the area to be treated, and gas such as oxygen inflates the bag to the desired gas pressure. The device contains a gas inlet for charging and a gas pressure release valve which is constructed for a fixed single maximum gas pressure. Unlike earlier hyperbaric devices, the device of this patent does not require a constant supply of gas. Although it is known that there are different narrow optimum pressures ranges for treating arterial wounds and venous wounds, the Topox bag is not designed to operate at a specific prescribed pressure. The devices cannot be adjusted to an optimum pressure in response to a wound diagnosis.
Dyson-Cantwell U.S. Pat. No. 5,478,310 discloses a hyperbaric oxygen chamber for use on leg wounds. It comprises a polyethylene bag to be secured around the leg and ages supply line. This device does have a pressure control means but it is connected to the gas supply line. As shown in FIG. 3, the chamber may have a tape covering holes in the gas bag that can be pulled off the holes during treatment to decrease gas pressure. Using this device it is difficult, if at all possible, to set and maintain the treatment pressure within the range of desired treatment pressure.
The prior art also discloses numerous topical hyperbaric devices that apply a continuous supply of gas flowing through the wound area. These of course require continuous connection to the gas supply, eliminating patient mobility during treatment.
Some of these prior art continuous flow devices have pressure control valves that are connected to and control the gas input See Stivala U.S. Pat. No. 4,224,921; Tramell U.S. Pat. No. 5,029,479; and Frech U.S. Pat. No. 4,772,259.
Pressure control means connected to the gas supply have several disadvantages. When the gas supply is disconnected or shut off the pressure control means is disconnected or shut off; and so the pressure control means is no longer functional. This is particularly important for devices designed for static treatment use. Also, accurate control of the treatment zone pressure is difficult because such valves are not directly measuring the treatment zone pressure. Furthermore, putting a pressure control valve in the gas supply line requires using an additional device, in addition to the gas cylinder or hospital gas supply line. In such a device the gas supply line cannot be directly connected to the hyperbaric treatment device treatment zone.